Turn the oven to broil, place the bell peppers directly on greased grates and cook until it's blistered and slightly blackened;

Meanwhile add 3 tbsp. of olive oil on a large frying pan and cook onions, stirring frequently until golden;

Remove the bell peppers from the oven and place them in a plastic bag to sweat;

Move the onions to the large sauté pan, wipe the frying pan;

Cut zucchini and eggplants in cubes;

Add 3 tbsp. of olive oil to the frying pan and cook the zucchini until soft. Move them to the sauté pan with the onions, wipe the frying pan;

Add 3 tbsp. of olive oil to the frying pan, add eggplants and cook until soft;

Move the eggplants to the sauté pan with the onions and the zucchini;

If you are using the fresh ripe tomatoes, cut a small cross through the skin on the base of each tomato, immerse it in the boiling water, blanch for 1 minute, remove with slotted spoon and peel away the skin. Cut them into quarters;

Add 2 tbsp. of olive oil to the frying pan, put the quartered tomatoes or tomatoes from the can to the frying pan, add the garlic, tie the celery stick and the bay leaves with a kitchen string together and add them to the tomatoes. Season with salt and pepper, cook for 20 minutes;

While your tomato sauce is cooking, remove the bell peppers from the plastic bag, peel, seed and cut into stripes. Add the bell peppers to the sauté pan with eggplants and zucchini;

Add tomato sauce to the sauté pan with vegetables, stir, adjust seasoning and cook on low heat for 20 minutes;

Remove the celery stalk and bay leaves and stir in chopped basil leaves.